溶胶—凝胶法制备掺钛U02微球工艺和性能影响因素研究

针对溶胶—凝胶法制备掺钛UO2微球中出现的掺钛凝胶微球粘连严重、烧结过度、微球抛光面腐蚀等现象,通过改进工艺条件和参数来解决工艺中出现的问题.结果表明:增加胶凝时间不仅能解决凝胶球的挤压变形问题,而且能大大改善凝胶球的粘连问题;降低烧结温度可以得到表面更加光滑的烧结体;选用浓硝酸(ω=68％)和高纯H2O(二者体积比为...     

内胶凝法制备HTGR燃料芯核

用内胶凝工艺研制了高温气冷堆(HTGR)燃料芯核,对该工艺的各个过程,如:缺酸硝酸铀酰(Acid Deficient Uranyl Nitrate)溶液和溶胶液的配制,分散溶胶成液滴并胶凝成固体微球、洗涤、干燥、煅烧,还原烧结等过程进行了系统的研究,并在1kg 级装置上进行了条件最佳化试验,确定了最佳工艺参数。本工艺制备的 UO_2燃料芯核密度达98%理论密度以上 O/U 比为2.000±0.005,圆球度(D_(max)/D_(min))达1.03,破碎强度为2kg,闭孔尺寸为1μm 左右。各项性能符合我国10MW HTGR 燃料元件的要求。     

注凝成型制备UO2陶瓷燃料核芯

高温气冷堆采用UO2微球作为燃料核芯,目前的主要制备方法采用溶胶凝胶工艺.为简化工艺流程、减少废液量,本工作研究采用注凝成型工艺制备UO2陶瓷微球.研究表明该工艺具有工艺简单、废液量少等优点.分析了溶胶凝胶和注凝工艺过程中的化学变化,研究了影响陶瓷微球直径的因素.采用该工艺制备出的UO2微球平均直径为710 μm,n(O)/n(U)≤2.01,密度为10.70 g/cm3.     

UO2-(Zr0.8Ca0.2)O1.8面心立方固溶体微球制备工艺研究

为研制出耐辐照的新型单相陶瓷燃料,采用溶胶-凝胶法,通过复合溶胶配制、分散胶凝、洗涤、干燥煅烧与烧结过程,开展了UO2-(Zr0.8Ca0.2)O1.8燃料微球制备工艺研究,制备出铀摩尔分数含量分别为30mol%、50mol%、70mol%的UO2-(Zr0.8Ca0.2)O1.8燃料微球样品。在对工艺过程进行分析的基础上,通过实验确定了工艺参数。采用X射线衍射（XRD）对3种燃料微球样品进行分析,分析结果表明:铀摩尔分数含量分别为30mol%、50mol%、70mol%的UO2-(Zr0.8Ca0.2)O1.8燃料微球样品均为面心立方（FCC）固溶体结构。      

高温堆嬗变Pu燃料元件的制备

介绍了清华大学在制备高温气冷堆嬗变Pu惰性元件方面的研究进展.分别采用溶胶凝胶工艺和注凝成型工艺制备ZrO2陶瓷微球作为基体,经过低温烧结获得多孔微球;用U代替Pu进行浸渍后,再经过高温烧结获得致密的陶瓷微球;基体中的U含最基本稳定在10%左右.采用与10MW高温气冷堆燃料元件包覆颗粒相同的制备工艺,在ZrO2/U复合微球表面依次沉积疏松热解炭、致密热解炭、SiC和外致密热解炭,制备出包覆型嬗变燃料颗粒.     

掺钛UO2微球烧结行为研究

采用溶胶-凝胶方法制备掺钛UO2微球,并通过金相显微镜、扫描电镜(SEM)、能谱分析仪(EDS)等观察掺钛微球的微观组织、气孔分布、晶粒大小、钛元素分布以及用水浸渍法测量其密度.实验结果表明:在一定烧结温度下,掺入少量钛可明显提高烧结性能.在实验条件下,最佳掺钛量为0.3％(质量分数)以内、烧结温度为1250-1350...     

外胶凝法制备高温气冷堆UO2核芯的湿法工艺

为制备高温气冷堆用燃料致密UO2核芯,对传统的溶胶-凝胶法进行优化和改进。主要对改进后的外胶凝工艺的湿法部分进行介绍,包括U3O8粉的溶解即欠酸硝酸铀酰(ADUN)溶液的制备、胶液的制备、胶液的分散和胶凝及凝胶球的陈化、洗涤和干燥等,并对湿法过程的机理进行了探讨。采用这一工艺,所得重铀酸铵微球的球形度好、尺寸分布均匀且具有良好空隙结构,经过后续的干法工艺如焙烧、还原和烧结,可制备出合格的高温气冷堆用燃料致密UO2核芯。     

制备致密UO2核燃料芯核的外胶凝方法（Ⅱ）

文章研究了用凝胶-支撑沉淀法制备密实UO_2包复颗粒芯核的干燥、煅烧和还原烧结三个阶段操作,分析了干燥方法、煅烧温度、中间产物的氧铀比、还原烧结温度以及升温速度对最终产品的影响,确定了UO_2致密化过程的最佳参数。小球密度达理论密度95%以上。     

乳液法制备微米级硅气凝胶小球及其表征

以硅溶胶为前驱物，在以吐温85和司班80为乳化剂、正丁醇为乳化助剂、正庚烷为分散介质的油相和二氧化硅醇溶胶为水相的乳液体系中，应用乳液成球技术制备μm级硅凝胶小球，然后通过常压干燥技术制备μm级硅气凝胶小球。用光学显微镜、SEM、TG-DTA及BET技术等对其进行表征。结果表明：所得μm级硅气凝胶小球表观粒径约为130μm，密度约为360kg·m^-3，比表面积为382.5m²·g^-1，平均孔径约为17nm，孔隙率达83.6%。μm级硅气凝胶小球是由大小约为10nm的二氧化硅纳米微粒构成的轻质纳米多孔结构材料。     

制备致密UO_2核燃料芯核的外胶凝方法(Ⅰ)

文章研究了一种由UO_2(NO_3)_2溶液制备高温气冷核反应堆燃料芯核(φ200±20μm)的外胶凝方法,由UO_2(NO_3)_2、尿素、NH_4NO_3、水、聚乙烯醇、四氢糠醇、乙二醇组成的溶液,经振动喷咀分散成液滴后,先后在氨气和氨水中固化成微球。设计和控制几何因子、物理因子、极限流量、振动频率等四项参数,可获得均匀分散的胶滴。固化后的湿球经陈化、洗涤后即可缓慢干燥。此方法简单、湿球强度好。     

ADVERTISING FOR PROFESSIONAL

The Shanghai Synchrotron Radiation Facility （SSRF） is a third generation of intermediate energy light source, belonging to a major state scientific engineering project. It consists of a 100 MeV linac, a 3.5 GeV booster, a 3.5GeV electron storage ring and a dozen of beamlines and experiment stations. As a huge public scientific research platform, SSRF will be a powerful tool for scientific research in the fields of physics, chemistry, life, material, environmental and geological sciences as well as information technology, microelectronics, micro/nano-meter technology, etc.     

ADVERTISING FOR PROFESSIONAL

The Shanghai Synchrotron Radiation Facility （SSRF） is a third generation of intermediate energy light source, belonging to a major state scientific engineering project. It consists of a 100 MeV linac, a 3.5 GeV booster, a 3.5GeV electron storage ring and a dozen of beamlines and experiment stations. As a huge public scientific research platform, SSRF will be a powerful tool for scientific research in the fields of physics, chemistry, life, material, environmental and geological sciences as well as information technology, microelectronics, micro/nano-meter technology, etc.     

基于Windows环境的动力堆核材料数据库计算机管理系统

报道了在Ｗｉｎｄｏｗｓ环境下建立的动力堆核材料数据库计算机管理系统。介绍了系统组成、特点及主要功能，主要描述了物理分析、软件数据流、用户处理基本流程等的系统设计方法。较之以往的工作，本系统增加了关键测量点及组件方位图布局的交互设置，增强了在多种动力堆运行参数情形下的适用能力；增加了数据库编辑、文本编辑、代码查看和设置功能；能自动衡算产生有关报表和管理文件，支持多种打印设备，有报表打印预览显示；具有数据加密、解密及数据备份恢复功能。     

肾-膀胱排泄的剂量学模型

计算有效剂量时，膀胱有0．05的组织权重因子值，为计算摄入放射性物质对膀胱壁产生的当量剂量，需要放射性物质经肾－膀胱排泄的剂量学模型，ICRP53号出版物给出了该模型的数学表达式。不过，这些表达式只适用于能从体液直接经尿排泄的物质，本文导出了摄入放射性物质 经体内若干器官，组织依次转移然后经尿排出时，其在肾尿路，膀胱内容物中衰变数的计算式，并以吸入99mTc标记的DTPA气溶胶为例，说明计算式的实际应用。     

INFORMATION FOR OVERSEAS CONTRIBUTORS

A three-field model was developed and implemented into the one-dimensional components of TRAC-M/F90 version 3782 for a better estimation of entrainment phenomena. The divide and conquer algorithmic technique was adjusted for the implementation after considering the verifications. The governing equations were composed of the conservation equations of each field with thermal-equilibrium assumption between the two liquid fields. In the development of the momentum equation for an entrained droplet, two different kinds of approaches were tested: the simple force balance on a single droplet and the field-type equation based on the continuum assumption. The first showed unstable nature and the latter was chosen. All of the necessary empirical correlations were obtained from literature, in particular the physical models of COBRA-TF.

The sensitivities of each empirical correlation were investigated where the effect of droplet diameter and droplet drag was found to be negligible. The advantages of the SETS numerical scheme in comparison with the semi-implicit numerical scheme were addressed in the simulation time and the maximum allowed time-step size. Finally, the simulations of Collier and Hewitt's experiment and Würtz' experiment were performed. In the simulations of Collier and Hewitt's experiment, the RMS error of entrained liquid flow rate and pressure gradient were 16.5 and 9.6%, respectively. In Wurtz' experiment, the predicted values agree with the measured ones with the RMS error of 2.8% in entrained liquid flow rate.     

INFORMATION FOR OVERSEAS CONTRIBUTORS

Experiments on the separation of H₂-HD isotopic gas mixture were performed with a 1,020 mm-height “Cryogenic-Wall” thermal diffusion column with a heated tube of 9.63 mm-outer-radius and a cooled tube of 14.21 mm-inner-radius which was cooled by liquid nitrogen. Abandance ratios of HD to H₂ in the feed, product and waste flow were measured by stable isotope mass spectrometer Finnigan MAT252.

Our rigorous numerical code has predicted dependence of separation factors obtained experimentally upon the operating pressure fairly well.     

INFORMATION FOR OVERSEAS CONTRIBUTORS

The challenges China is facing in energy security are briefly discussed. Then, the development of nuclear power in China in the first half of 21^st century is envisioned, and it is expected that Generation-3 PWR nuclear power plants (NPPs) would be the leading units of nuclear power in the coming 30–40 years. As part of the nuclear power program, the R&;D work on nuclear fuel cycle is generally described.